Question

An object is kept at a distance of 1m from a lens of power +2D:

1. Identify the type of lens.
2. Calculate its focal length and distance of the image formed.

Answer 1

1. The given lens is convex because convex lenses have a positive power.
2. P = `1/"f"`

        +2 = `1/"f"`

       f = +0.50 m

Its focal length is +0.50 m.

Using the relation = `1/"f"=1/"v"-1/"u"`

`1/"v"=1/"f"+1/"u"`

= `1/0.5+ (-1)/1`

= `(2+(-1))/1`

v = 1 m